The overall goal of this proposal is to develop a better understanding of the mechanisms underlying protein transport into olfactory sensory neuron (OSN) cilia. Cilia are complex, microtubule-rich, organelles uniquely adapted for diverse cellular functions. Defects in cilia structure and function have been shown to underlie a number of human diseases. Sensory cilia on dendritic endings of OSNs compartmentalize signaling molecules, including cyclic nucleotide-gated (CNG) channels that are the primary targets of odorant-induced signaling. Olfactory CNG channels are responsible for the translation of the chemical signal from the odorant receptor into action potentials that are processed in the brain. Despite a wealth of knowledge about CNG channel structure and function, little is known about the mechanisms of their subcellular targeting. Movement of proteins within the cilia is governed by intraflagellar transport (IFT), an evolutionary conserved process that facilitates movement of cargo along cilia and flagella. In mammalian systems, the heterotrimeric Kinesin II plays a clear role in IFT;however, a role in ciliary transport has not yet been established for the homodirrieric KIF17. Newly published experiments I performed in Dr. Martens'laboratory have shown that KIF17 is required for ciliary enrichment of the olfactory CNG channel in a heterologous system;however, the role for KIF17 in native olfactory epithelium remains unknown. Recently it has been shown that the proper targeting of another ciliary protein, nephrocystin 1, in nasal respiratory epithelial cells requires the binding of phosphofurin acidic cluster sorting protein 1 (PACS-1). PACS-1 is an intracellular sorting protein that binds to phosphorylated serine residues contained in a cluster of acidic residues on the cargo protein. PACS-1 has been shown to interact with several other acidic cluster-containing ion channel, however no role has been defined for PACS-1 in olfactory cilia transport. It is my hypothesis that the ciliary targeting of olfactory CNG channels is dependent on both KIF17 and PACS-1 in native olfactory epithelium. The following specific aims are designed to test this hypothesis: Specific Aim 1: To investigate the role of KIF17 in the ciliary transport of the olfactory CNG channel in native olfactory sensory neurons. Specific Aim 2: To determine the effects of PACS-1 on CNG channel ciliary targeting. I will address these aims using confocal imaging, assays of olfactory function, and viral expression systems. My proposal provides a plan to further elucidate the mechanisms of ciliary enrichment of the olfactory CNG channel. Characterizing the general mechanisms of channel targeting will provide a better understanding of ciliary transport and give us further insight into the underlying etiologies of human ciliary disorders.